Premagnetized magnetic pulser



June 8, 1954 P. E. K. DUFFING 2,630,820

PREMAGNETIZED MAGNETIC PULSER Filed April '7, 1951 Flyz 1 0/ f/vcfi Kan/Du {20/2 7 Inventor:

Patented June 8, 1954 UNITED STATES PATENT OFFICE PREMAGNETIZED MAGNETIC PULSER Application April 7, 1951, Serial No. 219,827

Claims priority, application Germany May 26, 1950 3 Claims.

My invention relates to magnetic devices for issuing an electric impulse in a given phase dependency upon the cycle period of a periodic or alternating current, such pulsers being used, for instance, to provide a contact device or an electronic tube with a control pulse at the moment when an alternating current passes through the zero point or through another predetermined instantaneous magnitude.

Known pulsers of this type have a ferromagnetic core, preferably of a substantially rec tangular magnetization characteristic, equippedwith a main winding to be traversed by the controlling current and with an impulse winding to issue the pulses. If the magnetic circuit of the pulser is not premagnetized, the pulse is always produced upon occurrence of a current zero passage of the alternating current flowing through the main winding. If it is desired to produce a pulse already at the instant of the zero passage or earlier, or if the pulse is to be produced when the primary current passes through a predetermined finite magnitude, then a premagnetization of the ferromagnetic pulser circuit by direct current or alternating current can be applied to achieve such a performance. The more closely the magnetic characteristic of the iron or other ferromagnetic material of the core approaches an ideal rectangular curve shape, the more accurate is the pulse transmission.

The application of premagnetization, however, has the disadvantage that the current in the premagnetizing winding of the pulser must be stabilized. That is, this current must not be changed by the reversal of magnetization caused in the magnetic circuit by the current flowing in the main winding. Consequently, relatively large resistors must be inserted in the electric circuit of the premagnetizing winding. lhe device has also the disadvantage that fluctuations in premagnetizing voltage affect the premagnetizing current and cause a phase variation of the pulser relative to Wave of the main current.

It is the general object of my invention to improve magnetic pulsers toward elimination of these disadvantages. To this end, and in accordance with a feature of my invention, I provide the ferromagnetic circuit structure of the pulser with a magnetic gap, particularly an air gap, of slight magnetic resistance and join with that circuit structure a permanent magnet so that its poles contact the structure at both sides of the gap, the portion of the ferromagnetic circuit structure that carries the main and pulse windings being saturated by the flux thus supplied by the magnet.

These and other features of the invention will be more fully understood from the following description in conjunction with the drawings in which:

Fig. l is explanatory and represents a magnetic pulser not in conformity with the invention for elucidating the essential features of the invention by comparison with Fig. 2 which illustrates, by way of example, a pulser embodying the features of the invention.

In Fig. 1 a torodial core l of a pulsing device is joined with a permanent magnet 2 to form a closed magnetic circuit together with the magnet and to receive premagnetizing flux from the magnet. The core I carries the main winding 3 of the pulser to be traversed by the primary alternating current, and a pulser winding 4 in which the pulses are to be induced in a given phase relation to the wave of the alternating current. If, as shown in Fig. 1, the permanent magnet is directly inserted into the iron circuit so as to form part of the ferromagnetic pulser circuit, two difiiculties are encountered. In the first place, the permanent magnet is apt to lose its flux due to the reversal in magnetization of the iron core I caused by the alternating flux induced therein by the current in the main winding 3. Furthermore, the permanent magnet greatly affects the magnetic characteristic of the entire magnetic circuit so as to produce a wide hysteresis loop unsuitable for the above explained purpose of pulse transmission.

It is, therefore, essential for the invention that the ferromagnetic circuit of the pulser be interrupted by a reluctance gap, such as an air gap, whose reluctance value is slight i. e. small enough to avoid appreciably changing the magnet characteristic of the circuit. It is furthermore essential, that the permanent magnet be joined with the magnetic circuit at both sides respectively of the gap so that the larger portion of the permanent magnet flux traverses the air gap and only a very small flux portion serves for the premagnetization of the iron core. In such a device, a reversed magnetization of the permanent magnet, due to the current flowing in the main pulser winding, is avoided because the flux within the permanent magnet suffers only negligable variations when the iron core is reversely magnetized by the main current.

The pulser shown in Fig. 2 is in accordance with the just mentioned features. The ferromagnetic circuit as a whole is again denoted by I. The iron core structure forming this circuit carries a main winding 3 and a pulse winding 4. The core structure has an air gap 5 of a slight magnetic resistance so that the magnetic characteristic of the magnetic iron circuit is essentially determined by the magnetic characteristic of the limbs 6 of the core structure, this characteristic being approximately rectangular. The permanent magnet 2 has its two pole surfaces joined with the iron core at opposite sides respectively of the air gap 5. The winding 3 is connected in a circuit energized from an alternating-current supply or source '5.

When the main pulser winding 3 is deenergized, the permanent magnet 2 passes most of its magnetic flux through the air gap 5 while a substantially smaller flux portion traverses the limbs G of the ferromagnetic core structure. The flux through the limbs, however, is sufiiciently large, relative to the material and cross section of the limbs, to cause saturation of the iron in these limbs. The cross section of the air gap 5 and of the immediately adjoining portions or" the core is substantially larger than the iron cross section of the limbs so that a saturation of these adj oining core portions is avoided despite the large magnitude of the flux in the air gap.

When the current in main winding 3 has such a direction that it tends to augment the flux of the permanent magnet in the limbs 5, the abovementioned conditions are not affected because the limbs are already saturated. However, when the current in the main winding flows in the opposite direction, the flux in the limbs ii is reversed. When the current, before reaching the zero passage, drops below a predetermined instantaneous value, the driving force of the permanent magnet will preponderate and produce a flux reversal in the limbs of the iron core. This flux reversal causes a pulse to be induced in the pulse winding s. A pulse is also produced when the flux in the iron limbs is first produced by the permanent magnet and is then reversed under the action of the main current.

To permit the adjusting of the premagnetization, magnetic shunts may be placed across the poles of the permanent magnet. A similar effect can be obtained also by varying the air gap.

It will be understood by those skilled in the art upon a study of this disclosure that the shape and other design of pulsers according to the invention may be modified and that such pulsers may be equipped with auxiliary or accessory windings other than those mentioned, without departure from the essence of the invention and within the scope of the claims annexed hereto.

I claim:

1. A premagnetized magnetic pulser for issuing electric pulses in a given phase relation to a periodic current, comprising a ferromagnetic core structure having a substantially rectangular magnetization characteristic, said core structure forming a substantially closed magnetic circuit and having a gap, a permanent magnet having pole faces of difierent magnetic polarities joined with said core structure at opposite sides respectively of said gap to pass premagnetizing flux through said structure, said structure having a first portion extending continuously between said two pole faces and being saturated by said flux,

iii

and said s ructure having two unsaturated other portions extending between said respective pole faces and said gap, said two other portions and said gap having a larger cross section than said first portion, a source of alternating current, a primary winding connected with said source and disposed on said first portion for periodically desaturating said first portion, and a secondary winding disposed on said first portion to produce periodic pulses at the desaturating moments.

2. A premagnetized magnetic pulser for issuing electric pulses in a given phase relation to a pcriodic current, comprising a ferromagnetic core structure having a substantially rectangular magnetization characteristic, said core structure forming a substantially closed circuit and having four serially joined limbs forming together a substantially rectangular shape, one of said limbs on one of the narrow sides of said rectangular shape having a larger flux-traversed cross section than the other three limbs and having a gap parallel to the adjoining two limbs, a permanent magnet having two pole faces of different respective magnet polarities, said pole faces extending parallel to said gap and being joined with said structure on opposite sides respectively of said one limb and along respective junction areas larger than said cross section of said other three limbs, said magnet having a flux below the saturation value oi said one limb and above the saturation value of said other three limbs, a source of alternating current, a primary winding connected with said source and disposed on said first portion for periodically dcsaturating said first portion, and a secondary winding dis posed on said first portion to produce periodic pulses at the desaturating moments.

3. A premagnetized magnetic pulser for issuing electric pulses at a given moment prior to the zero passage or" an alternating current, comprising a ferromagnetic core structure consisting of a material or an approximately rectangular magnetization characteristic, said structure forming a substantially closed magnetic circuit and having a gap of slight reluctance, a permanent magnet having two pole faces joined with said structure on both sides respectively of said gap to pass premagnetizing flux through said structure, a main winding and a secondary winding disposed on said core structure, alternating-current supply means connected with said main winding for producing a voltage pulse in said secondary winding when the current in said main winding declines below a given instantaneous value, said main winding having relative to said magnet and relative to said supply means the poiing at which the flux caused by said main winding is opposed to said permanent-magnet flux at the beginning of said pulse.

Refer Cited in the file of this patent UNITED STATES PATENTS Number Name Date 2,169,866 Bedford Aug. 15, 1939 2,324,634 McCreary July 20, 1943 

